A book in which a Victorian detective recorded his conviction that he knew the real identity of Jack the Ripper, but would go to his grave unable to prove it, was loaned yesterday by his great grandson to Scotland Yard's infamous Black Museum.

Long after the country was convulsed by the butchery of a succession of poor women in Whitechapel, east London, Chief Inspector Donald Sutherland Swanson added a long handwritten note to the margin and back pages of a memoir published in 1910 by his friend and colleague Assistant Commissioner Robert Anderson. The murderer was a mentally ill Polish man called Aaron Kosminski, Swanson wrote, suspected after an attack on his sister who was covertly brought by the police to "the Seaside Home"- the police convalescent home at Brighton - for an unofficial identify parade. He added that the only man who could identify Kosminski would never give evidence "because the suspect was also a Jew, and also because his evidence would convict the suspect and (sic) witness would be the means of murderer being hanged which he did not wish to be left on his mind". Swanson wrote that Kosminski had died in a mental asylum: in fact if he has been correctly identified in the hospital records, the unfortunate man lived on until 1919.

Swanson took over the shambolic investigation of the murders that were terrifying and thrilling Victorian England. Yesterday Detective Chief Superintendant Steve Lovelock said he gave "considerable weight" to his predecessor's final conclusions on the case.

The museum, more properly known as the Crime Museum, is world famous for its gruesome memorabilia of some of the most infamous murders of the last two centuries, including the cooker used by Dennis Nilsen to render down the victims he killed at 195 Melrose Avenue.

The collection began in the 1870s and has moved three times with the headquarters of the Metropolitan police, and has just been re-displayed.

The curator, Alan McCormick, said yesterday it was a serious teaching tool for young police officers. It has never been open to the public though thousands of visitors including the Queen Mother and Charlie Chaplin have been given guided tours.

Other candidates proposed as Jack the Ripper have included Queen Victoria's grandson Prince Albert Victor, Duke of Clarence, who died in an 1891 flu epidemic and Lewis Carroll, creator of Alice In Wonderland. In the past decade the American crime writer Patricia Cornwell has spent a small fortune of her own money trying to prove that the artist Walter Sickert was the Ripper.

"There isn't a shred of evidence against Kosminski," Keith Skinner, one of the most diligent researchers of Ripper material said yesterday, "there is absolutely no material evidence against any of the suspects."